1. Field of the Invention
The present invention relates to an image communication apparatus for receiving image data from an external device via a network and a method for controlling the image communication apparatus.
2. Description of the Related Art
To communicate information among remote offices, image data is transmitted and received using facsimile machines. The facsimile machines transmit and receive image data over a public switched telephone network (PSTN) using a protocol in conformance with ITU-T T.30.
In addition to using facsimile machines, recently, image data has been transmitted and received using an e-mail by attaching the facsimile-based image data to the e-mail in accordance with the protocol in conformance with ITU-T T.37. In this communication method, since data is transmitted and received via an Internet protocol (IP) network, image data can be transmitted and received at a cost lower than that required for the facsimile communication in accordance with the protocol in conformance with ITU-T T.30.
Furthermore, a real-time Internet facsimile communication (hereinafter referred to as “IP-FAX communication”) has been developed in which facsimile data is transmitted and received in real time via an IP network using an ITU-T T.38 protocol. More specifically, a facsimile machine at a transmission side is directly connected to a facsimile machine at a reception side via an IP network so that a facsimile signal in conformance with ITU-T T.30 is converted to TCP/IP packets and is transmitted and received.
In the above-described IP-FAX communication, the call control procedure based on ITU-T H.323 is employed. Recently, session initiation protocol (SIP), which is similar to ITU-T H.323 protocol, has garnered increased attention.
When comparing the call control procedure in conformance with ITU-T H.323 with SIP, ITU-T H.323 protocol is more complicated since ITU-T H.323 includes a variety of sub-protocols. In contrast, SIP defines only basic session control sub-protocols, such as sub-protocols for starting, changing, and ending a session. Accordingly, SIP is relatively simplified. Consequently, SIP is highly flexible and can be easily integrated into other systems.
SIP includes a user agent, which is a user terminal (e.g., an IP telephone), and a SIP server. The term “SIP server” collectively refers to a proxy server, a redirect server, and a registrar server. Therefore, for example, the alternative address of a facsimile machine on a reception side can be registered using the redirect server.
More specifically, in the case where a particular facsimile machine on a reception side is specified as a destination address of image data, another facsimile machine is registered with a redirect server as a forward address of the image data. Thus, when a facsimile machine on a transmission side transmits image data to the particular address, the alternative address is read out from the redirect server. Subsequently, a call connection is started so that a connection between the facsimile machine on a transmission side and a facsimile machine at the alternative address is established. The facsimile machine on a transmission side then transmits the image data to the facsimile machine at the alternative address (refer to, for example, Japanese Patent Laid-Open No. 2005-94662).
However, in the case where, as described above, an alternative address is registered with the redirect server and image data is transferred, the following problem arises. That is, when the facsimile machine at the transmission side sends a call request to a facsimile machine located at the address specified by the user, the call request command is forwarded to the facsimile machine located at the alternative address. Thus, a connection with the facsimile machine located at the alternative address is established and, subsequently, the transfer of the image data is started.
At that time, the facsimile machine located at the alternative address, which is specified as a forward address, cannot determine to which address the image data was originally transferred from the facsimile machine at the transmission side. That is, the facsimile machine located at the alternative address cannot determine whether the image data was originally destined for it or another facsimile machine.
That is, the user of the facsimile machine located at the alternative address cannot determine whether the received image data is destined for the facsimile machine of the user or not. Accordingly, ease of use of the facsimile machine is significantly degraded.
In addition, Japanese Patent Laid-Open No. 2005-94662 describes a facsimile machine that, when the facsimile machine transmits image data after changing the destination address of the image data to the alternative address, adds a mark to the image data to be transmitted, indicating that such an operation has been performed. By using this mark, a user of the facsimile machine on the reception side can determine whether the received image data is originally destined for it or another facsimile machine. However, if the facsimile machine on the transmission side does not add the mark indicating that the image data has been transmitted to the alternative address, the user of the facsimile machine on the reception side cannot determine whether the received image data was originally destined for it or another facsimile machine.